Stress, depression and memory decline.

Undoubtedly the most important study on depression for a very long time was published this week. For the first time the causal link was established between stress—in our time this is mainly work stress—and depression.

Depression is associated with impaired recollection. People who are depressed have poor memory for positive events, and enhanced memory for negative events, but the relevant neural mechanisms are poorly understood. This is the focus of this new study in the journal Trends in Neurosciences.

What the researchers found. Stress is a common trigger of nearly all initial depressive episodes, and chronic (ongoing) stress can prevent new cells being formed in the hippocampus—the brain’s memory center—to replace those that have died off. This stress can also, they found, inhibit mesolimbic dopamine neurons (thus prevent sufferers from feeling pleasure), and sensitize the amygdala’s response to negative information. The amygdala is the main fear center of the brain and this sensitization tends to make people feel anxious and fearful and more likely to look for what’s wrong rather than what’s right.

So what? As our society becomes increasingly stressful the rate of depression increases. Some recent studies have shown that up to 30% of employees suffer from episodes of major depression. That is up from about 8% or so fifteen years ago. The stress produced by the way we are forced to work—including open plan offices and the like, the fear of job loss, the isolation of working from home, over work, being “on” via smartphone 24/7—is a major stressor. We are simply not designed to cope with it. Now we know for sure that this is, quite literally, killing us through the stress/depression nexus (often disguised as psychosomatic illness or very real heart disease).